In these years, in disk apparatuses such as magnetic disk apparatuses, the density of data stored on a disk medium tends toward being made higher. Accordingly the track pitch of the disk medium tends toward becoming narrower. It is desired to more accurately control the position along an cross-track direction of the head when reading out data from a disk medium of a narrower track pitch by a head. The head positioning control is performed based on servo information items dotted along a circumferential direction.